Effect of Nitrogen and Harvest Aid Applications to Soybeans
White Papers about adding nitrogen [N] fertilizer to soybeans and using harvest aids for improved soybean harvest have been posted on this website. The below narrative provides a summary of recent research pertaining to these two management practices.
An article titled “Soybean response to nitrogen fertilizer in different soils” by Vonk, Nafziger, and Fontes appears in the Crop Forage & Turfgrass Mgmt. online journal. A summary of the conduct of and results from the research reported in this article follow.
• The research involved conducting nine field experiments in Illinois between 2014 and 2017. Soybeans were planted in May at all locations in all years.
• Urea N fertilizer was broadcast on the soil surface at planting, R1, R3, or R5, and at all four times.
• Over the range of soil types and environments in this study, there was rarely an increase in soybean yield as a result of N application.
• In the few cases where soybean yield was increased by the addition of N fertilizer, the yield increases were not sufficient to cover N fertilizer costs.
• The authors concluded that the addition of N fertilizer at planting might be advantageous on fields that support limited early-season growth.
• The results from this research support the findings from other research–i.e., adding N fertilizer to soybeans is not economical even if yield increases result from the practice.
An article titled “Impact of application volume and spray droplet size on soybean harvest aid efficacy” by McNeal et al. also appears in the above journal, and provides the following information about how harvest aid spray applications affect efficacy of applied harvest aid materials.
• In 2019 and 2020, field experiments were conducted at three locations in Miss. to evaluate the impact of application volume and spray droplet volume mean diameter [VMD] on the efficacy of soybean harvest aids that included paraquat, saflufenacil [Sharpen], and sodium chlorate.
• The efficacy of applied harvest aids was not affected by application volumes of 5 and 20 gal./acre.
• Desiccation efficacy of paraquat was superior to that of the other two harvest aids used in the study.
• Small differences in efficacy did occur among VMD’s of 200, 500, and 800 µm, but the differences were deemed inconsequential by the authors.
• Soybean seed yield did not vary due to any combination of harvest aid, VMD, or application volume.
• The authors recommend that paraquat be used as a component of a harvest aid that may be applied to soybean.
• According to these results, applications of soybean harvest aids are not sensitive to the application volumes or spray droplet sizes used in this study. These results also confirm that paraquat is the most effective harvest aid product to apply to soybeans.
It is recognized that the subjects of these two papers are not connected as management practices for soybeans. However, these cited results confirm what is known from previous research with N fertilizer and harvest aid applications that are highlighted in the aforementioned White Papers.
Composed by Larry G. Heatherly, Sep. 2024, larryh91746@gmail.com